The melt log started as a maintenance record — batch weights, temperatures, which cullet went in. Somewhere around melt nine we started numbering finished pieces against it, and now it’s the first thing collectors ask about.
A piece stamped MELT 31 shares actual chemistry with every other piece from that melt: same batch, same trace impurities, same slight color lean. That’s not marketing. It’s the closest thing glass has to a vintage.